Aliases for spacing basics

Hello - an dev ergonomics request! Would it be possible to add more terse aliases for spacing/sizing values, e.g. `extraExtraSmall` => `xxSmall`. We were thinking of adding this in *our* layer but thought we'd ask if other devs would also prefer something that requires a bit less typing.

Start by reviewing the existing spacing and sizing values and their naming conventions. Determine whether terse aliases such as `extraExtraSmall` => `xxSmall` should be supported consistently, then define the accepted aliases and how completion will be verified.

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